Can we destroy an artificial general intelligence without its consent?
Firstly, an AGI could conceivably exhibit all of the observable properties of intelligence without being conscious. Although that may seem counter-intuitive, at present we have no physical theory that allows us to detect consciousness (philosophically speaking, a 'Zombie' is indistinguishable from a non-Zombie - see the writing of Daniel Dennett and David Chalmers for more on this). Destroying a non-conscious entity has the same moral cost as destroying a chair.

Also, note that 'destroy' doesn't necessarily mean the same for entities with persistent substrate, i.e. their 'brain state' can be reversibly serialized to some other storage medium and/or multiple copies of them can co-exist. So if by 'destroy' we simply mean 'switch off', then an AGI might conceivably be reassured of a subsequent re-awakening. Douglas Hofstadter gives an interesting description of such an 'episodic consciousness' in "A Conversation with Einstein's Brain"

If by 'destroy', we mean 'irrevocably erase with no chance of re-awakening', then (unless we have a physical test which proves it is not conscious) destroying an entity with a seemingly human-level awareness is clearly morally tantamount to murder. To believe otherwise would be substrate-ist - a moral stance which may one day be seen as antiquated as racism.